The invention concerns a linear guide with a guide rail on which a guide carriage is supported for movement longitudinally, and with a drive causing longitudinal motion of the guide carriage which is constructed as an electric motor with a motor element arranged on the guide rail and with a motor element arranged on the guide carriage, as well as a distance-measuring system assigned to the linear guide which has a measuring strip adjacent to the guide carriage or the guide rail running parallel to the guide rail, and a measuring head movable relative to this.
Moreover the invention concerns a linear guide with a guide rail arranged in a guide housing on which a traveling carriage is supported for movement longitudinally, and with a drive causing the longitudinal motion of the traveling carriage which is constructed as an electric motor with a motor element arranged on the guide rail and a motor element arranged on the traveling carriage as well as with a distance-measuring system assigned to the linear guide.
A linear guide with a distance-measuring system is also known from the publication WO 91 16 594. With the device described there, a measuring strip is installed in the material of an elongated carrier which is inserted into a rectangular groove of a guide rail and fastened by gluing. On a guide carriage movable along the guide rail, a measuring head is arranged such that it is adjacent to the measuring strip.
Publication DE 198 42 384 A1 shows a linear guide of the type mentioned at the beginning where the guide reals and the guide carriage are arranged in a guide housing constructed as a beam. The electric drive with the motor component of the guide rail and the motor component of the guide carriage is situated in this so that it forms a linear motor.
For regulation of a linear motor, using high resolution optical measuring systems is known. These are sensitive to dirt and represent a high cost factor. Magnetic or inductive linear measuring systems are also known as economical linear measuring systems. These cannot be so high resolution as, for example, optical linear measuring systems due to physical conditions. Especially with linear motors, the speed signal necessary for regulation must be calculated or differentiated on the basis of the linear measuring system. If the resolution of the system is not high enough, then the entire drive becomes unsteady and therewith unusable.
Underlying the invention is the object of creating an improved, economical linear guide which is less sensitive toward dirt accumulation.
This objective is accomplished in accordance with the invention in that the distance-measuring system is assigned an acceleration sensor operating with an eddy current sheet and an exciter block surrounding this. In this way, obtaining a speed signal can be realized though the acceleration sensor. The latter can be a sensor operating according to the Ferraris principle whereby the eddy current sheet consists of a non-magnetizable metal sheet and the exciter block contains permanent magnets. A Ferraris sensor only measures the relative acceleration between two structural components moving in relation to each other. It is possible with these sensors to operate a linear motor with a low resolution but economical magnetic or inductive linear measurement system. By integration of a linear measurement sensor and a Ferraris acceleration sensor in a mounting channel guide, the advantages emerge that no additional structural space is necessary, that a diminution of the installation expenditure and costs savings take place, and that an interchangeability of linear measurement systems becomes possible.
The function of the eddy current sheet can be assumed by the guide rail, and this can be made of an anti-magnetic hardenable roller bearing element. A non-magnetizable metal material can also be used as an eddy current sheet which is installed in an elongated groove of the guide rails.
The exciter block can be constructed U-shaped and be arranged in a separate housing which is fastened to the guide carriage. Here the housing for the exciter block can be arranged in a face of the guide carriage pointing in the direction of motion. Moreover, the measuring head of the distance-measuring system can be arranged in a housing which is likewise fastened to the guide carriage on a face pointing in the direction of travel.
According to a further proposal, the objective is accomplished in accordance with the invention in that the distance-measuring system is assigned an acceleration sensor with an eddy current sheet and an exciter block operating according to the Ferraris principle, whereby the eddy current sheet consists of an electrically conducting non-magnetizable material and the exciter block contains permanent magnets. In this way, obtaining a speed signal can be realized through the acceleration sensor. The eddy current sheet can form part of a cable channel for a drag chain of the beam U-shaped in cross section. This results in the advantage that with a linear guide with a cable channel for a control device containing the acceleration sensor, no additional structural space is necessary, and that in this way costs can be saved in installing the linear guide.
The beam can be fastened on a long side of the guide housing. The exciter block can be constructed U-shaped in cross section, and the eddy current sheet can be partially surrounded by the exciter block. This can be held by a driver strap which is fastened on a long side of the traveling carriage. Aluminum or copper, for example, come into consideration as an electrically conducting, non-magnetizable material for the eddy current sheet.